1. Field of the Invention
The present invention relates to a vehicle pneumatic tire having a patterned tread, a belt brace having, e.g., multiple layers, bead areas having bead cores, and a single- or multi-layer constructed carcass having at least essentially radially running strength supports. The carcass is designed to run around the bead cores and to run back into the sidewalls as a turn-up. Further, in the unloaded and unpressurized condition of the tire, as well as when the tire is mounted on a rim, the positioning of the profile of the carcass deviates from that of an equilibrium figure.
2. Discussion of Background Information
A tire similar in general to that discussed above is known, e.g., from GB-A 2 024 738. To avoid undesired deformations and stresses on belt edges, it is suggested to design the belt layers in a specific manner for the purpose of influencing the carcass profile in the unpressurized or nearly unpressurized condition as compared to the carcass profile under internal pressure.
British Patent 1 576 409 relates to increasing the load-carrying capacity of a vehicle pneumatic tire without having to accept losses in comfort or undesired heating of the tire. For this purpose, it suggests designing the sidewalls or the carcass with a comparably slight curvature and preventing it from returning under internal pressure to a more bulbous shape. For this purpose, the belt brace is designed by providing special belt layers to be very resistant against bending moments in the circumferential direction.
It is common and has also been state of the art for a long time to determine or calculate the contour of the carcass in the tire, which also usually at least approximately corresponds to the sidewall contour, at a given internal pressure as a function of the carcass length in the sidewalls. When so doing, the heating mold for the tire is also designed in such a way that, if possible, it does not cause any changes in the contour of the carcass or the contour of the tire sidewalls, starting from the contour determined by the heating mold up to the contour that the tire assumes in mounted condition under internal pressure. For such a design, it is known that the carcass is positioned according to its neutral. This is intended to avoid unnecessary stresses in the tire due to changes in shape. In the tread area, tires also usually have a contour curved in the crosswise direction, so that when deflecting under internal pressure and load, the contact pressures acting within the driving surface, the area of the tire touching the ground, are compensated to the extent possible, which is necessary for force transmission and to constitute the desired load-carrying capacity. This curvature, like the curvature of the carcass in the sidewall areas, is predetermined by the tire shape but, in the finished product, it is also a function of the design of the strength-giving elements, e.g., strength supports in the belt and in the carcass.
When the carcass contour is positioned in a neutral manner, a carcass profile often results in the flattened condition in which the forces caused by the internal pressure are transferred relatively strongly to the shoulder areas of the ground contact surfaces. Therefore, the contact pressure distribution within the driving surface is no longer compensated to the desired extent, which can impair a series of tire properties, e.g., abrasion, noise level, and driving and braking behavior on wet and dry surfaces.
A number of ideas for which patent applications have been filed or that are protected by patents deal with the optimum design for the outside contour of vehicle pneumatic tires, e.g., EP-A1 0 269 301, and with measures by which the pressure of the tire in the ground contact surface and/or the contour of the ground contact surface itself are to be influenced, e.g., to reduce rolling resistance or to achieve more even abrasion. In that regard, reference is made, e.g., to EP-B1 0 323 519. The known measures usually involve a design for curvature of the tire in the tread area.
The present invention provides the desired compensated contact pressure ratios within the part of the tire touching the ground, the driving surface, by measures involving the positioning of the carcass. As a result, a positive influence can be had on braking behavior on wet and dry surfaces, noise level, and abrasion behavior.
Accordingly, the carcass, in an area between a binding point to the belt and a binding point to the rim, is formed with a length that is shorter than the theoretical length of the carcass between those points, which results from the equilibrium figure.
The measures according to the invention have a pronounced beneficial effect on the desired compensated pressure ratios in the ground contact surface of the tire. The shorter carcass reduces in the shoulder areas the extent of the transfer of forces exerted by the tire internal pressure and thereby produces uniformity of the pressure ratios in the contact surface. Under internal pressure, the tire sidewalls are in fact deformed in such a way that the tire becomes wider in comparison with its unpressurized condition and, in a zenith area, grows somewhat and thereby acts against growth in the belt edge areas and, in particular, even a reduction of the distance from the belt edges to the bead occurs.
In particular, the design is such that the length of the carcass between the two connection points corresponds to about 80 to 97%, in particular about 85 to 95%, of the theoretical length in those areas determined in accordance with the equilibrium figure. It is precisely within those areas that the most compensated possible pressure distribution in the ground contact surface of the tire can be achieved.
In that regard, it is also advantageous when, in the unpressurized and unloaded condition of the tire while it is mounted on a rim, the mean radius of the carcass is greater than the mean radius of a carcass positioned according to the equilibrium figure. This corresponds to a xe2x80x9cstraighterxe2x80x9d positioning of the carcass profile.
Tires designed according to the invention are preferably simultaneously designed in such a way that the alternating tensile and compression stresses in the turn-ups of the carcass, which are detrimental for various tire properties, can be avoided. For this purpose, in the unpressurized, unloaded condition of the tire while it is mounted on a rim, the carcass in the area between the binding point to the belt and the point having the largest cross-sectional width has one radius or multiple radii which together are smaller than the radius or radii in those areas of the carcass that run between the point having the largest cross-sectional width and the binding point to the rim.
Therefore, when the tire rolls under load, only fluctuating tensile stresses act in the turn-ups of the carcass, for whose size and distribution over the turn-up of the carcass it is beneficial if, in the unpressurized, unloaded, and mounted condition of the tire, the ratio of the smallest radius of the carcass to the largest radius of the carcass is between about 1:1.1 and 1:2.2, in particular between about 1:1.4 and 1:2.0.
For optimum distribution of the fluctuating compression stresses in the area of the carcass turn-up, it is advantageous in this regard if, in the unpressurized, unloaded, and mounted condition of the tire, the radius of the carcass is smallest in the area of the binding point to the belt and largest in the area of the binding point to the rim, such that the radius of the carcass continuously enlarges between those two points.
The present invention is directed to a vehicle pneumatic tire that includes a patterned tread, a belt brace including at least one layer, bead areas having bead cores, and a carcass having at least one layer, which is arranged through the sidewalls, around the bead cores, and back into the sidewalls as turn-ups. The carcass and the belt brace are coupled together at a belt binding point, and a radially outmost portion of the bead area is adapted to contact a rim forming a bead binding point between the carcass and the bead area. The carcass, in a region between the belt binding point and the bead binding point, is formed with a length shorter than that of a theoretical carcass between the belt binding point and the bead binding points determined in accordance with an equilibrium figure.
In accordance with a feature of the invention, the length of the carcass and the theoretical length of the carcass are determined for a tire in an unpressurized condition and when the tire is on the rim.
According to another feature of the present invention, the carcass may include at least essentially radially running strength supports.
In accordance with still another feature of the instant invention, the length of the carcass between the binding points may be about 80 to 97% of the length of the theoretical carcass between the binding points. Preferably, the length of the carcass between the binding points may be about 85 to 95% of the length of the theoretical carcass between the binding points.
According to another feature of the invention, in an unpressurized, unloaded, and mounted condition of the tire, a mean radius of the carcass can be greater than that of the theoretical carcass.
In an unpressurized, unloaded condition of the tire while it is mounted on a rim, the carcass, in an area between the belt binding point and a largest cross-sectional width point, can have a radius of curvature which is smaller than a radius of curvature of the carcass between the largest cross-sectional width point and the bead binding point. Further, in the unpressurized, unloaded, and mounted condition of the tire, a ratio of the radii of curvature, from smallest radius to largest radius, may be between about 1:1.1 and 1:2.2, and preferably, the ratio of the radii of curvature may be between about 1:1.4 and 1:2.0. Still further, in the unpressurized, unloaded, and mounted condition of the tire, the radius of curvature of the carcass can be smallest in a region of the belt binding point and largest in a region of the bead binding point, and the radius of curvature between the belt binding point region and bead binding point region may continuously increase.
In accordance with another feature of the present invention, the belt can include a plurality of layers.
The present invention is directed to a process for forming a vehicle pneumatic tire that includes a patterned tread, a belt brace including at least one layer, bead areas having bead cores, and a carcass, having at least one layer. The process includes arranging the carcass through the sidewalls, around the bead cores, and back into the sidewalls as turn-ups, such that a portion of the carcass extends at least from a belt binding point, at which the carcass is coupled to the belt, to a bead binding point, which is a radially outmost portion of the bead area that is adapted to contact a rim. The process also includes forming the portion of the carcass with a length which is shorter than that of a theoretical carcass between the belt binding point and the bead binding point determined in accordance with an equilibrium figure.
In accordance with a feature of the invention, in an unpressurized, unloaded condition of the tire while it is mounted on a rim, the process may further include forming the carcass, in an area between the belt binding point and a largest cross-sectional width point, with a radius of curvature which is smaller than a radius of curvature of carcass between the largest cross-sectional width point and the bead binding point. In the unpressurized, unloaded, and mounted condition of the tire, a ratio of the radii of curvature, from smallest radius to largest radius, may be between about 1:1.1 and 1:2.2, and preferably the ratio of the radii of curvature can be between about 1:1.4 and 1:2.0. Still further, in the unpressurized, unloaded, and mounted condition of the tire, the process can further include forming the carcass such that its radius of curvature is smallest in a region of the belt binding point and is largest in a region of the bead binding point, wherein the radius of curvature between the belt binding point region and bead binding point region continuously increases.
The present invention is directed to a vehicle pneumatic tire that includes a patterned tread, a belt brace including at least one layer, bead areas having bead cores, and a carcass having at least one layer, which is arranged through the sidewalls, around the bead cores, and back into the sidewalls as turn-ups. The carcass and the belt brace are coupled together at a belt binding point, and a radially outmost portion of the bead area is adapted to contact a rim forming a bead binding point between the carcass and the bead area. The carcass, in a region between the belt binding point and the bead binding point, is formed with a profile different than that of a theoretical carcass between the belt binding point and the bead binding points determined in accordance with an equilibrium figure.
According to a feature of the invention, the profile of the carcass between the binding points can be flatter than that of the theoretical carcass between the binding points.
In accordance with yet another feature of the present invention, a length of the carcass between the binding points may be shorter than that of the theoretical carcass between the binding points.